Hydraulic tappet



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Reissued Nov. 19, 1935 HYDRAULIC TAPPET Charles E. Johnson, North Muskegon, Mich.

Original No. 2,006,641, dated July 2, 1935, Serial No. 634,857, September 26, 1932. Application for reissue September 25, 1935, Serial No. 42,167

4 Claims. (Cl. 123-90) of the same general nature as that disclosed in are provided for automatically taking up all my copending patent application led Jan. 11, 1932, Serial No. 585,859, in which hydraulic means clearance between the valve tappet and the valve stem and the principal object of this invention is to provide means for eliminating air which inadvertently enters the hydraulic pressure medium such as oil used in the pressure lubricating system of the automobile.

In the customary installation of a device of this nature in an internal combustion engine the conventional'pressure lubricatingsystem is utilized to` furnishoil under pressure to the hydraulic means provided in the valve tappet and the small amounts of air which become mixed with the oil are detrimental to the perfect operation of the valve tappet. The device depends for its operation upon the incompressible quality of oil and inasmuch as air lacks that quality and is compressible, when any considerable, amount of it is contained in the oil within the valve tappet, it will permit relative movements of the parts which should not occur in perfect operation and for that reason it is desirable to eliminate the air which inadvertently enters with the oil into the hydraulic means of the valve tappet.

The invention provides various novel features of construction and arrangement as hereinafter f more fully described and particularly pointed out in the claims, reference being had to the accompanying drawing, in which,

Fig. 1 is a vertical section of a portion of a conventional internal combustion engine showing a poppet valve, a cam and a valve tappet embodying this invention in operative position.

Fig. 2 is an enlarged elevation, partially in section, of a valve tappet embodying this invention shown in lowered position in its guide.

Fig. 3 is a fragmentary section of the upper portion of the parts shown in Fig. 2 showing the valve tappet in raised position in its guide.

Fig. 4 is a. sectional plan view on the line 4-4 of Fig. 3, and

Fig. 5 is a sectional plan view on the line 5-5 of Fig. 3.

Like reference numbers refer to like parts in all the figures.

I represents the engine casting which is provided with a valve opening 2 and a poppet valve 3 is arranged to close the opening 2 having a conventional seat at the edge of the opening. 'I'he valve stem. 4 passes through a valve stem guide 5 and is provided with a. valve spring 6 which spring seats at its upper end against a fixed part of the engine and at its lower end on a. spring seat 'I fastened to the valve stem 4. A cam 8 on a cam shaft 9 is located below the valve stem 4 and a valve tappet is interposed between the cam 8 and the lower end of the valve stem 4.

The tappet comprises a body I0 which is mounted for vertical sliding movement in a` tappet guide VII. The upper end of the tappet body I0 is provided with an axial opening in which is located a slidable plunger I2. A check valve cage I3 is located in the opening below the plunger I2, said opening being of slightly reduced diameter at the location of the cage and the cage being of exteriorv diameter to provide a press t into said reduced portion of the opening. The cage has an axial opening I4 which is reduced to provide a seat I5 for the ball check valve I6 and lateral openings II are provided below the ball I6 which communicate-With lateral openings I8 which extend through the body I0 of the tappet and communicate with an annular groove I9 therein.

A small rod or pin 20 extends across the opening I4 of the cage a short distance above the ball I6 to limit the movement of the ball in a direction away from its seat. A passage 2| is in communication with the oil pressure lubricating system of the engine and leads to the inte- "rior of the tappet guide I I at a point where it will communicate with the annular groove I9 inthe tappet body so that oil under pressure will be conducted into the interior of the tappet body through the passages I8 and I1 and past the ball check valve IG.

As previously stated. the valve tappet is interposed between the cam 8 and the lower end of the valve stem 4 and it is of proper length that when the slidable plunger I2 is in retracted or lower position and when the cam is in position to lower the tappet, there will be a slight space or clearance between the upper end of the plunger I2 and the lower end of the valve stem 4. The plunger is moved upwardly relative to the tappet body which acts upon the lower end of the plunger.

Movement of the plunger is limited by a retainer which is in the nature of a ring 22 surrounding the upper end of the tappet body I0 and having an end 23 projecting inwardly into an annular groove 24 in the plunger I2. The width or vertical dimension of the groove 24 is sufficient to permit movement of the plunger I2 within the desired operating range but will prevent movement of the plunger beyond that range especially in an upward or outward direction. The plunger in its downward or inward movement may be stopped by the end 28 o! the retainer ori' the lower end of the plunger may engage against the upper end of the valve cage I8 as shown in Fig. 3.

A central opening 28 is provided in the plunger extending upward from its lower end into which theoilwillriseandalsoanyairwhichmaybe contained in the oil will rise into this opening 2l by reason of the differences in speciilc gravity and at the upper end of the opening 28 a small outlet opening 28 is provided which extends through the body of the plunger and communicates with an annular groove 21 in the outer surface of the plunger.-

A passage 28 is provided through the wall of the tappet body I8 ina position where it will communicate with the -groove 21 when the plunger is in lower position but said groove will be out of communication with the passage 28 when the plunger is raised. The outlet opening 28, the groove 21 and the passage 28 are for the purpose 'of permitting the escape of air from the interior of the device and it may be here stated that the air will escape from the passage 28 between the tappet III and the tappet guide II since there must be some looseness or clearance in the ilt of the tappet in the tappet guide for proper operation, such clearance being sumclent to permit the escape of small quantities of air which are to be eliminated. However, the clearance is not suillcient to permit any material quantity of oil to escape from theinlet passage 2l and thus the oil pressure will be transmitted.

to a point underneath the plunger I2 to cause its upward. movement.

Operation with the interior of the tappet I8 which permits the plunger I2 to recede or lower causing a gap between the upper end of the plunger and the lower end of the valve stem. Immediately upon beginning operation of the engine a pressure is attained in the pressure lubricating system of the engine and also within the valve tappet which causes the plunger to rise into close engagement with the lower end o! the valve stem. The pressure of the oil in the system is not sufiicient to raise the valve spring 8 but will act to litt the weight of the plunger I2 until it is stopped by` engagement with the valve stem 4.

'I'he oil to produce this lifting action has entered from the passage 2i into the annular groove I8 and thence passes through the passages i8 and I1 -and past the ball check valve I8 into the interior of the tappet body I8 and the ball check valve I8 prevents return movement of the oil and traps the oil which has entered to hold the plunger I2 to the position to which it has been extended because o! the incompressibility of the oil. Action ci the cam 8 tqraise the tappet body then lifts the valve I compressing the valve spring 8, this action being exerted through the plunger I2 and the oil trapped under it within the tappet body.

The upward movement of the plunger to engage with the valve Astein has caused the groove 21 to move out of communication with the passage 28 and therefore prevents the escape oi' oil through the outlet opening 28. As the engine operates the cam repeatedly lifts the tappet I and then lowers it causing a similar action of the valve 8. During the period when the cam holds the tappet in raised position a considerable force is applied downwardly on the plunger I2 but ths force is resisted by the oil trapped be low the plunger by the ball check valve I8. Dur- 1o y ing the intervals between the raised position of the tappet and when the valve 8 rests upon its seat, there is no downward thrust by the valve against the plunger I2 and the pressure vof the lubricating system is sumcient to renew the supl5 ply of oil under the plunger i2 to take the place of any leakage which may have occurred by supplying additionaloil under pressure past the ball check valve I8 and thus the plunger I2 is maintained in constant engagement with the valve stem 8 during the operation of the engine.

The foregoing description of the operation is as it would occur providlng that there were no air mixed with the oil in the space below the plunger I2 and above the ball I8. Entrance of 25 air mixed with the oil into that space in any appreciable quantity will cause the oil, so mixed with air, to have the quality ci beingcompressed. When this occurs the considerable force exerted downwardly upon vthe plunger I2 when the cam 80 8 raises the tappet will cause the plunger I2 to lower within the tappet body because ofthe compressible quality of the oil mixed with the air, to a position shown in Fig. 3 which will cause communication between the groove 21 and the 35 passage 28 permitting the escape of air or corr bined oil and air from the interior of the tappet.

It is assumed that the air will separate from the oil to a large extent, by reason of the differences in their specicgravity, and rise to the top o! the opening 28 so that the air will be expelled through the opening 28 and the oil within the tappet body cleared from its ai'r content within a reasonably short time. During each interval of lowered tappet position the part of the contents of th interior of the tappet which has been expelled as described through the outlet 28 will be replenished by oil injected past the ball valve I8 Vand when substantially all of the air has been separated from the oil, which oil will be then incompressible. the plunger will not lower to communicate the groove 21 with the passage 28 and no further escape of the contents of the interior of the tappet body will occur.

With this construction it will be seen that so long as clear oil unmixed with air is contained within the tappet body its incompressibility will hold the plunger I2 in'raised position in which the groove 21 will not vcommunicate with the paage 28 and the oil will be positively trapped 60. within the tappet body excepting for such small leakage as may occur, either around the plunger I2 or past the ball valve I8. Any entrance of .air into the tappet chamber in suflicient quantities to permit yielding of the plunger I2 in a down- 05 ward direction will automatically cause communication between the groove 21 and the passage 28 whereby such air will be expelled through the outlet opening 28 and the expelled air will be replaced by additional oil supplied at the rest position of the tappet.

. 'I'he invention has been described as embodied in a tappet for operating the poppet valve o! an internal combustion engine but it is conceived that the same invention will be applicable to part is to be moved by action of another part and wherein clearance between the parts is to be eliminated and especially where there may be an alteration in the dimensions of the parts due to change of temperature, wear, etc., which would make a permanent adjustmentimpossible, a device made `in accordance with this invention is applicable.

It is also conceived that other sources oi' pressure than the pressure lubricating system of an engine may be utilized to supply iluid under pressure to the device and its operation. Even when the tappet is used in an internal combustion engine having a pressure lubricating system it may be desirable to supply tluid pressure for the tappet mechanism by some other suitable means.

It is to be understood, of course, that the tappet will" probably be used in multiple in an internal combustion engine, one 'tappet being used ior each valve and that when so used a common source oi uid under pressure supplies all oi the tappets.

The invention is dened in the appended claims and is to be considered comprehensive of all forms of structure coming within their scope.

.I claim:

l. A device oi' the class described comprising, a body having an interior opening, a plunger -slidably mounted in said body and extending into said interior opening, means for supplying oil into said interior opening to extend said plunger, a second means for carrying away air from said interior opening, and a third means controlled by movement oi' said plunger for closing the second means when the plunger is extended and for opening the same when the plunger is retracted.

2. A tappet comprising, atappet body having a normally vertical axis, an axial opening extending into said tappet body from the upper end thereof, a plunger extending into said axial open- 19,761 other devices. In any mechanism in which one ing and vertically movable therein, means for feeding oil into said axial opening below said plunger, means for trapping oil ted into said axial opening, a recess in the lower end of said plunger, an outlet passage in the plunger communicating 5 with the upper portion of said recess, and a passage through the tappet body in a position to communicate with said outlet passage in the plunger when the plunger is in relatively retracted lower position and to be out of communication 10 with said outlet passage when the plunger is in extended raised position.

3. A tappet comprising, a tappet body having an axial opening extending through the upper end of said tappet body, a plunger slidably l5 mounted in said axial opening, means for introducing oil into said axial opening, below said plunger. check valve means for trapping oil introduced into said axial opening, an opening in said plunger extending upwardly from the lower 20 end thereof and closed at its upper end, an annular groove in the outer surface of said plunger,

a passage communicating between said annular groove and the upper portion o! said opening in the plunger and a passage through the wall of 25 said tappet body located in a position to com municate with said annular groove when the plunger is in relatively retracted lower position, said annular groove being out oi communication with said passage in the tappet body when the 30 plunger is in relatively extended raised position.

4. A valve tappet oi' the class described comprising, a. tappet body having an interior opening, a plunger slidably mounted in said tappet' body and extending into said interior opening, pressure means for introducing oil into said interior opening to extend said plunger and outlet vmeans leading lirom said interior opening, said plunger rendering the outlet means inoperative at a certain predetermined range of positions. 40

CHARLES E. JOHNSON. 

